1. Technical Field
The present disclosure relates to a MRI (magnetic resonance imaging) apparatus and a magnetic resonance imaging method which magnetically excites nuclear spins of an object with an RF (radio frequency) signal having the Larmor frequency and reconstructs an image based on NMR (nuclear magnetic resonance) signals generated due to the excitation, and more particularly, to a magnetic resonance imaging apparatus and a magnetic resonance imaging method which make it possible to perform MRA (Magnetic Resonance Angiography) in which a blood flow image is acquired.
2. Related Art
Magnetic Resonance Imaging is an imaging method which magnetically excites nuclear spins of an object set in a static magnetic field with an RF signal having the Larmor frequency and reconstructs an image based on NMR signals generated due to the excitation.
In the field of MRI, MRA is known as a method for obtaining an image of a blood flow. MRI without using a contrast medium is referred to as non-contrast MRA. As non-contrast enhanced MRA, an FBI (fresh blood imaging) method synchronized with an ECG (electro cardiogram) signal captures a pumping blood flow ejected from the heart, thereby satisfactorily representing a blood vessel (for example, refer to Japanese Publication of Patent Application No. 11-239571).
As related technology used with the FBI method, an ECG-prep procedure measures an appropriate delay time for synchronization with an ECG signal. The ECG-prep scan is a preparation scan used to decide upon an appropriate delay time for synchronization with an ECG signal and is performed prior to an FBI scan for imaging. The FBI scan is subsequently performed using the ECG delay time decided upon by the ECG-prep scan. The ECG-prep scan obtains plural single-shot images at mutually different time phases by acquiring data at gradually changed delay times from an R wave of an ECG signal. By selecting an ECG-prep scan image in which blood vessels are appropriately depicted from among the plural ECG-prep scan images, the ECG delay time for the FBI scan can be determined. This allows a high velocity blood flow to be depicted at a time phase corresponding to a lower flow velocity.
As a technology for selecting the most appropriate ECG-prep image from the plural ECG-prep images acquired by the ECG-prep scan, FBI-NAVI is also devised (for example, refer to Japanese Publication of Patent Application No. 2008-23317).
However, there is a problem in that it is conventionally difficult to determine the delay time for ECG synchronization, i.e., a time phase as an imaging timing without reference to ECG-prep images by a skilled operator.